<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
    <script>
        let arr = [2,4,6,8,9,7,5]

        function sum(a){
            let gentle = 0
            let odd  = 0
            for(let i =0 ;i < a.length;i++){
                if(a[i] % 2 !==0){
                    gentle += a[i]
                    odd += 1
                }
            }
            if(odd === 0){
                document.write(`0`)
                return
            }else{
                document.write(`平均数是${gentle / odd}`)
            }
        }
        sum(arr)
    </script>
</body>
</html>